Help! I’m working on a project with my son for his 8th grade class. The object is to design something to time one minute. Points are given for creativity and accuracy. No sand or pendulum devices are allowed. Anything using water must be unconventional and creative. I don’t think fire is allowed either.
I have to admit that I’m not an engineer with good ideas on this one. We have been trying to come up with something for over a week with zero success. I normally don’t ask the whole world to help with homework, but I guess I am going to make an exception here.
My web page is “Pete’s Excellent Home Page” Please check it out! Make sure your sound is turned on!
It is dedicated to Paris and Pinball information and pictures http://www.geocities.com/zpinaddict
Why not make a fancy Rube Goldberg (SP?!) device that lasts one minute? Keep adding and subtracting things until it is just right.
I was in the Science Olympiad in high school and they had an event that required making these devices and they would have to perform certain tasks at certain times, and of course only last a certain time. Roll a golf ball down a few ramps, have a motorized “elevator,” and make it all last 60 secs.
Take a really long board and mount a flashlight on one end. On the other end of the board, 11,178,000 miles away, mount a light sensor. Turn on the light and wait for the sensor to register, at which point a minute should have passed.
Seriously, the first thing that comes to my mind is some sort of gravity based device. Think of the game “Mousetrap”, but on a bigger scale. Mount it all on a large board, and make sure that the surface is level to reduce fluctuations in the time.
If this is to be done inside, look for windows that are far away from an inside wall. Watch and measure the shadow as it moves.
Does your son’s school have a gymnasium? With windows? Print out some paper with different increments on it, take a stop watch and find the proper increment.
Or possibly, use the flag pole outside. The light will be very diffused, but, it might work.
Thanks for getting me to think about something else.
Did you ever see those things at the mall where you place a quarter in a chute which then rolls on edge into a giant funnel, round and around, finally into the base?
You could make a giant funnel out of cardboard reinforced with wood and either line it with plastic or paint it with an enamel/high-gloss paint. Create a little chute. Then you could use something fun like a superball or marble with the object being to drop out the bottom at the one-minute mark. There would be a lot of trial and error to get the shape right, but it could be fun.
Sponge (large pack of identical new sponges)
2 foot long x 2 inch wide piece of wood
clear plastic container
plastic tubing (like aquarium air hose tubing)
Rubber bands
coat hanger
plastic top to laundry detergent
hot melt glue gun
small clamp
Drill hole in middle of wood and using coat hanger wire or similar make a pivot point and support in the middle so it see-saws and is elevated. Attach it to a wood base.
Use rubber bands to affix sponge (wetted then thoroughly wrung out) to one end of wood see-saw. Screw or glue a small plastic cup (laundry detergent cup or similar) to other end of wood see-saw.
Take the clear plastic water container an drill or punch a very small hole in the bottom or side near the bottom. Using a hot melt glue gun put a clear aquarium hose into this hole and seal it.
Elevate the water container above the see-saw. Put pennies (or whatever) into the cup to weigh it down so the sponge is up in the air on the see-saw and the cup is down. Using the small clamp on the hose regulate the water flowing onto the sponge and by removing or adding weight to the cup gradually adjust the mechanism so that it takes 60 seconds of water flow to make the sponge heavy enough to tip the see-saw to the sponge side.
Teachers love bright colors so be sure to use lots of clear and colorful stuff wherever possible. Perhaps even dye the water red.
I live at a high altitude (11,200). I can watch the sun/shade slide across my floor. But I really have to concentrate. The distances between window and floor are about 20 feet.
The clear air at this altitude may have something to do with the fact that I can see this.
Think of a fulcrum, this is your window, the earth is spinning. The greater the distance from the fulcrum to your measuring device (read piece of graduated paper on the wall or floor) the greater your accuracy.
Problem. The greater the distance between the object that projects the shadow and the clock the more diffusion from the sunlight. Makes the “clock” hard to read.
Could a cardboard tube help here? How about a magnifying glass on the end of the tube? It should only focus while the sunlight hits the entire glass.
Have him give some of his classmates a task. Each have 5 bolts and nuts and they must pick them up and put them together.
See where I’m going. He could pick 3 friends, have them practice and see what kind results he can get by doing a task as fast as they can. Change the task or the amount of people for better accuracy.
[slight hijack]
At my Alma Mater, there is a sundial on the engineering quad that is accurate to within 30 seconds. It has a wheel to rotate the numbers based on the date, so even as the Earth changes in it’s orbit around the sun, it still shows the accurate time. It’s about 2.5 feet wide and 5 feet tall.
I know your son is required to build a device of some sort, but with practice it is possible to accurately time one minute intervals in his head. Feynman and company performed this experiement many years ago and they were consistently accurate to within a second or two.
I’m not a big fan of projects that encourage “creative” and unnecessarily complex solutions. Might be good for an art class, but science is supposed to teach you to look for the simplest, most practical and most accurate solution given the constraints.
My first thought was to put a string on a pulley, put a weight on one end and a disk with holes on the other. Put the disk at the bottom of a cylindrical container and fill it with oil or water. The weight will slowly pull the disk up. Mark how far it moves in one minute and you’re done. The only problem is, viscosity is highly sensitive to temperature. I’m not sure just how sensitive, so you’d have to experiment.
A sundial would be difficult. The sun is not a point source, so you can’t get a perfectly sharp shadow - that limits the accuracy. What you could do is use a telescope and project the image of the sun onto a piece of paper. Since it is a projected image and not a shadow, it will be very sharp. And since it is magnified, it will be easy to measure the movement. A cheap department store telescope should be sufficient. Half a pair of binoculars might work too, but the magnification may not be quite enough. Of course, you should not look through the telescope, even with a filter. The real question is, how are you going to make sure the weather is good on the day you need to demonstrate the device?
Alka seltzer tabs
Plastic soda bottle
Balloon
Electrical tape.
Put some water in the bottle.
Break up the alka seltzer and put it in the balloon.
Put balloon over neck of bottle and secure w/tape.
Lift balloon to dump alka seltzer into bottle.
Experiment until you can burst the balloon in (more or less) one minute
If you hum the Final Jeopardy tune twice, that’s a minute. (Helpful trivia for working in a darkroom making contact prints with a busted timer.)
I’m thinking a marble run would be fun. (Like what ZipperJJ (Rube Goldburg), and DMC (Mousetrap) said, only completely different to justify a new post.)
-Rue.
I’m thinking about water drip rates. Get a can and put a small hole in it so that it drips. Collect drops for one minute in a beaker with milliliter graduations. Check to see variance at different temperatures. Use the measured amount of water.
You could use a system to count the number of drips in a minute and then a set amount of water would not be required.
Another possiblity is the “mirror sundial”, which unfortunately isn’t portable.
You pick a south facing window (if you are in the northern hemisphere). You place a tiny mirror flat on the sill of the window, so that it shines a dot of light on the wall/ceiling of the room. Then you place marks or indicators on the wall/ceiling so as to tell the time.
The advantage is that one will have a large angular measure to play with, critical if one is attempting to measure an amount of time as short as one minute with a sundial.
Digital Voltmeter (Borrow this if you don’t already have one)
100 uF capacitor (Very cheap purchase at Radio Shack)
9V battery
Find out what the input impedance of the voltmeter is. For digital meters, it is usually 1,000,000 ohms or 10,000,000 ohms. Record this as “R”.
Charge capacitor with 9V battery by connecting them together for 5 seconds. The capacitor will be of the electrolytic type, so make sure you get the polarity correct.
Hook the voltmeter to the capacitor. Record the initial voltage as “Vo”. It should be around 9 V. Also, don’t touch the leads with your fingers. It’s not because you’ll get shocked (it’s perfectly safe), it’s because you are a resistor, and the capacitor will discharge faster if you touch the leads.
Keep the voltmeter connected to the battery. The capacitor will discharge into the voltmeter. While it is discharging, quickly calculate the following:
V(60) = Vo * exp(-600000/R)
The answer you get, V(60), will be the voltage at 1 minute. Note that exp(x) is the natural log of x.
EXAMPLE
Your voltmeter has an input impedance of 1,000,000 ohms. You charge the 100 uF capacitor with a 9 V battery. You hook the capacitor to the voltmeter. The initial voltage (Vo) is 9.0 V.
V(60) = Vo * exp(-600000/R) = 9 * exp(-600000/1000000) = 4.9 V.
Thus, you will know 1 minute has passed by when the voltage reaches 4.9 V.
